New Hampshire, USA --
Back in mid-August, Vine Fresh Produce in Ontario unveiled a 2.3-MW solar rooftop array on its greenhouse, the largest commercial rooftop project under the province's feed-in tariff (FIT). This system notably incorporates a technology that's been more familiar in the U.S. residential solar market: microinverters. (The devices, made in Enphase's Ontario plant, helped the project qualify for that FIT.) Weeks ago Enphase followed that up with another large-sized project using microinverters, 3.1-MW of distributed solar across 125 buildings for the San Diego Unified School District.

Those announcements were meant as stakes in the ground. "We've proven [microinverter technology] in residential, we're proving ourselves in small commercial... but our ambitions are much bigger than that," said Raghu Belur, Enphase co-founder and VP of products and strategic initiatives. "We're seeing people deploy [microinverters] in significantly larger systems."

The technology is rapidly gaining traction, according to Cormac Gilligan, IHS senior PV market analyst. Microinverter shipments will reach 580 MW this year, with sales topping $283 million, and average global prices sinking 16 percent to $0.49/Watt, he projects. By 2017 he sees shipments soaring to 2.1 GW with revenues of about $700 million, and expansion beyond the U.S. into several regional markets, especially those in early stages of development that might be more open to newer technologies: Australia, France, the U.K., Switzerland, and even Hawaii. Japan's big residential solar market is especially attractive, but poses certification challenges and strong domestic competition.

But as those two Enphase projects illustrate, there's another growth area for microinverters that's emerging alongside regional expansion — up into commercial-sized rooftop solar installations. The same reasons residential customers like microinverters apply to small-scale commercial projects as well: offset partial shading, more precise monitoring at the individual module level, provide a more holistic readout of what the system is producing, and improve safety because they typically use a lot lower voltage. Just nine percent of microinverter shipments in 2012 were to commercial-scale use, noted Gilligan — but he sees those surging to nearly a third of shipments by 2017.

Who’s Making Microinverters

The microinverter space is getting crowded (see table below), if not yet a model of parity. Enphase continues to dominate with more than half of the sector's revenues in 2012, four million units cumulatively shipped and four product generations. "We are a high-tech company that happens to be in the solar sector," Belur explained. Compared with what he called the "big iron, big copper guys" who are now broadening their inverter portfolios with microinverters, "we're all about semiconductors, communications, and software." The company designs its own chips for its microinverters, and outsources manufacturing to Flextronics.

SMA got its entry into the game with the 2009 acquisition of Dutch firm OKE. "In the residential market it became clear to us that customers were interested in the microinverter architecture," said Bates Marshall, VP of SMA America's medium-power solutions group. SMA also sells the string inverters that have gained favor over big centralized inverters, so SMA's simply broadening its portfolio. With the emergence of the U.S. solar end-market, SMA is more willing to push some R&D and product development over here; "we get to drive the bus to a greater extent," he said. SMA recently started shipping microinverters to the U.S. from its German inventories, but a production line is now being qualified at the company's Denver facility.

Similarly to SMA, Power-One (recently bought by ABB) aims to supply whatever type of power conversion capability customers need, noted Chavonne Yee, Power-One's director of product management for North America. So far demand for microinverters has come in the U.S. residential market, offering high granularity and maximum power point tracking (MPPT), but she sees most of the commercial-scale demand switching from traditional central inverters to three-phase string inverters, not microinverters.

Module supplier ReneSola sells a standalone microinverter, touting the typical features with some higher (208-240) voltage options for small light commercial, but at a 15-20 percent lower price point, explained Brian Armentrout, marketing director for ReneSola America. "We are seeing some demand" in small light commercial applications ranging from 50-kW up to 500-kW at which points there's "the breaking point where string inverters make more sense." Down the road the company wants to take the end-around route of integrating microinverters directly onto panels; its gen-2 microinverter should be available in the spring of 2014. Armentrout projects ReneSola will be "in the top three" next year for microinverter sales, while simultaneously aiming high for the top spot in module shipments.

Others are looking to integrate microinverters directly into the modules. SolarBridge has worked closely with SunPower and BenQ to design its microinverters to eliminate several components that typically fail, notably the electrolytic capacitors and opto-isolators, explained Craig Lawrence, VP of marketing. They also minimize other typical costs such as cabling, grounding wires and even tailoring the microinverter for a specific module type to optimize the microinverter's firmware, he explained. He sees the trend to bring microinverters into the commercial-scale environment, particularly with SolarBridge's more recent second-generation microinverters in the past year or so.

Microinverters vs. String Inverters

In general, installers are making a choice between microinverters and string inverters, comparing functionalities and costs. Both sides make a case for reliability: microinverters use fewer components and represent lower cost when something does fail; string inverter vendors point out microinverters have only been on the market for a few years and can't make substantial claims about reliability. IHS's Gilligan noted the sheer number of microinverter devices in the field potentially requiring repair/replacement could be daunting.

Anonymous's comment against Enphase and for SolarEdge is full of bias and inaccuracies. You are perfectly entitled to your opinion, but what you have put together here is quite off base. I don't have time to clarify in detail, but wanted to mention to any readers that they should do their research.

ANONYMOUS
December 25, 2013

To Bill, I think to answer your question about the "green House" it is now a Hot house for growing, looks like half day light , half solar. I bet it's pretty dark inside now, compared to before. The picture is deceiving , almost looked as if the entire roof was panels. Glad to see they did it tho. I'm at 17 kw now.

I believe in first place that any development in this direction it must be promoted and backed up for the sector´s members in benefit of the short, medium and long term real growth of PV technology as one of the most feasible alternatives as contribution into the equation ;
sustainability- cost - rationality.
The fastest the technology grows less damage for the community pocket and even skepticism as result of the generalized screwed up happening in some countries ( i would recommend the recent Spanish experience since yr. 2004-2013 for better understanding as the most frustrating case ).
In second place, I would recommend a sort of generalized consensus between the main active Countries promoting the PV market, and or Thermic Solar or any Recognized renewable technology , to assume and facilitate with the main Power companies actives in their Grid Systems that " sustainable energy it means an impact in the traditional way to handle the technical-economical balance in their systems and therefore their traditional economics results "
Considering that in most of the main Countries in the world the power markets had been controlled or managed as monopoly or oligopoly either under the States or Economics Groups .
USA is a singular case as market in the world and therefore the way that business decision are made in USA has nothing to do with the rest of the World.
Competitiveness, Legislatives Criteria or practices are positively far of the rest in other Continents.

I would recommend in benefit of a better understanding just to " make a comparative international wholesale and final consumer price per KWh".
After that just compare the amount of Companies per Market an the Internationalization of them....

Most probably after that exercise it would be easier to understand the difficulties for obtaining a real fair result for the final power consumers any where..( better possibilities in USA it is definitively clear)

Alberto Escobar

ANONYMOUS
December 25, 2013

With the pv panels facing south, I don’t see how enough light can get into the greenhouses to support plant growth. Have those greenhouses been taken out of service for growing?

Microinverter companies need to be able to accommodate AC-coupled inverters with battery storage. For example, Enphase presently does not allow this without potentially voiding the Enphase warranty, although the AC-coupled inverter system has complete UL-approval. The microinverters act as current source that will put out current into what they see as an infinite load: the grid. The AC-coupled units are designed to switch off the microinverters as a current source to the grid, through AC-inverter frequency upshift as battery voltage rises. In addition to this fail safe protection provided by AC-coupled inverters to prevent battery damage, various relay schemes have been used to take out groups of microinverters at preset AC-inverter frequency values to hold AC current down. The real solution should come from the microinverter manufacturers to develop microprocessors for their addressable units to shut off individual microinverters and keep the array charging optimally, yet avoiding damage to batteries, AC-coupled inverter, and microinverter.

ANONYMOUS
December 24, 2013

solar mounting: www.landpowersolar.com

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Jim is Contributing Editor for RenewableEnergyWorld.com, covering the solar and wind beats. He previously was associate editor for Solid State Technology and Photovoltaics World, and has covered semiconductor manufacturing and related industries,...

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